The present invention relates to a closure device and catheter assembly suitable for transcatheter operations, for example, operations for closing or repairing vascular defects or endocardiac defects such as ventricular septal defect.
At the present time, Fontan operations have been used for repair operations of complex cardiac anomalies such as single ventricle. In this operation, a single ventricle is used for the systemic circulation system, and for pulmonary circulation a vein of the systemic circulation system is directly connected to a pulmonary artery, whereby cardiac function is repaired. After this operation, however, a considerable decrease of cardiac output may occur because of increase of a pulmonary vascular resistance or transient ventricular hypofunction. The increase of pulmonary vascular resistance is caused by spasm of the pulmonary circulation system. The considerable decrease of cardiac output occasionally makes it is difficult to perform postoperative management.
In order to avoid the increase of pulmonary vascular resistance and the considerable decrease of cardiac output, it is general practice for the above operation to form a small fenestration or perforation of about 4 mm between atria (most cases, the interatrial septum is made of an artificial membrane), whereby allowing the blood to flow through the small fenestration or perforation. This procedure followed by formation of the small fenestration or perforation is a Fontan fenestration. The surgical operation is mainly carried out as a method of treatment for closure of the small fenestration after Fontan fenestration. However, this surgical operation is followed by thoracotomy of a patient in addition to the treatment of the affected area and thus it is a great burden to a patient. In particular, in case of child patient this burden is considerably large.
Percutaneous transluminal therapeutic catheterization is known as a noninvasive procedure for repairing endocardial defects. In this procedure, closure of atrial septal defect is carried out by transveneously inserting an intercardiac catheter into the heart, and the first clinical success is reported by King and Mill in 1976. In the procedure carried out by King et al, double disk-shaped or umbrella-like members for left and right atria are introduced into the atrium through an insertion tool composed of a double-layered catheter coaxially arranged on a core wire, and then united into one so that an interatrial septum is sandwiched in between the umbrella-like members to occlude the atrial septal defect (ASD). However, this procedure requires use of a very large-sized insertion tool and hard umbrella-like members, thus making it impossible to apply it to children, especially, to preschool children.
To solve this problem, Rashkind investigated miniaturization of the device and developed a plug of a single umbrella type with hooks to close atrial septal defects. A clinical success in child was reported in 1977. However, this procedure has another problem such that hooks of the plug are occasionally caught in an unintended site of the heart. Once the umbrella-like member is opened, the umbrella-like member can not change its position or withdraw from the hooked site, resulting in emergency operation. To overcome the above disadvantages, Rashkind further developed an improved plug comprising united double umbrella-like members. This plug is widely put into clinical use for occlusion of patent ductus arteriosus.
On the other hand, Lock et al developed a clamshell-shaped interatrial closure device by additionally incorporating a coil spring into a middle portion of each of eight stainless frames of the plug of Rashkind, as disclosed in Japanese patent application (Japanese unexamined patent publication No. 5-237128). This closure device is firmly fixed to the thin interatrial septum by closely adhering double umbrella-shaped members to each other in the overlapping state. Because of its configuration similar to the shell of a clam of a bivalve, this device is called the "clamshell-shaped septal occluder". The procedure is carried out by introducing an elongated sheath with a thickness of 11 French into the repair site through the femoral vein. This procedure is applicable to a patient with a weight of more than 8 kg and therefore widely used for closure of atrial septal defects by means of percutaneous transluminal therapeutic transcatheterization.
The closure treatment of the small fenestration after Fontan fenestration is done with the closure device as the percutaneous transluminal therapeutic transcatheterization.
However, if the closure treatment of the small fenestration after Fontan fenestration is performed with the closure device of the prior art, adhesion of thrombus may occur because of a large closure plate and there is a high risk of complications. Further, in cases where the closure device has fallen away or dislodged during operation, it is difficult to withdraw the closure device because of the shape or size of the closure device.